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| fly cutter |
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| wongster:
I found that I get nice finishes when the cutter is cutting at the trailing end of the circle. In my case, from right to left. Wong |
| cidrontmg:
No1_sonuk, Iīve also tried a similar round- tipped tool, an exact copy of yours. It works rather well with steel, ali, cast iron (chips fly even straight from the cast surface), less well with brass/bronze. The surface finish is rather scratchy, though. An HSS tool bit gives a better surface, but it must be really razor sharp. The classic test for a keen edge is to check if it will cut hair from the back of your hand. With a carbide tip, no chance. A sharp HSS bit, no problem. And in general, the ready-made fly cutter shanks have usually far too little an angle for a Bogs- style ground tool bit. The angle should be at least 20o, but it wonīt hurt any if itīs 40-50o. Obviously the sweep will get less with a steeper angle, and thereīs less "air" above the workpiece. :wave: |
| No1_sonuk:
Last night I discovered a flaw in my cunning plan... Be careful if you try fly cutting up to a shoulder using an insert lathe tool. Depnding on the design of the tool, the support behind the insert might not have enough clearance to get round. Mine didn't :doh: On the tool I showed above, the support goes straight down/back with no angle. It was designed as a lathe tool, which doesn't need a relief angle. Of course, one could always make or modify an insert holder specifically for the job with sufficient undercut. |
| Bogstandard:
Having read this post all the way thru, it seems I caused some confusion with regards to 'TOP'. If you actually go to the first page, and find where I put up the grind pics with the pretty red lettering on, directly under the last pic, I explain what is meant. Another couple of points that do need to be brought up. The radius of the cutter should be the width of the cutter blank, so for a 6mm blank, the radius should be 6mm, not elongated as some of you have done. The other point is the direction the faces need to be ground. The direction should be with the grind marks at right angles to the cutting face. Do the radius grind first, then the front of the cutting face. Doing it that way, you are doing just two grinds. You sharpen by rubbing your stone against the vertically ground angled face, not around the radius grind. I have done a C-o-C to try to explain what I mean. Bogs |
| wongster:
Hi Bogs, Glad to "see" you in here. Hope you're better. I did the radius about the size of the tool width but it seemed that the cutting action was at (or almost) the shank. So I "lengthened" the cutting edge but grinding it longer. It could be the angle of my holder being too shallow. Regards, Wong |
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